diff --git a/Sources/Model/IManager.cs b/Sources/Model/IManager.cs
index b408766..9b48bcf 100644
--- a/Sources/Model/IManager.cs
+++ b/Sources/Model/IManager.cs
@@ -8,6 +8,8 @@ namespace Model
 {
     internal interface IManager
     {
-
+        public T Add<T>(ref T toAdd);
+        public T Remove<T>(ref T toRemove);
+        public T Update<T>(ref T before, ref T after);
     }
 }